JP6954241B2 - Release paper base paper and release paper - Google Patents

Description

The present invention relates to a release paper base paper and a release paper using the release paper base paper.

The adhesive sheet is formed by forming an adhesive layer between the surface base material and the release paper, and in recent years, with the development of the information-oriented society, it covers a very wide range such as commercial use, office use, and household use. , Labels, stickers, stickers, emblems, delivery slips, etc. Paper is mainly used as the surface base material, and as the release paper, a release agent such as a silicone compound or a fluorine compound is applied to high-density base paper such as glassine paper, clay coated paper, polyethylene laminated paper, or the like. Is widely used. As the release agent, a solvent-free silicone resin is usually used in terms of release performance, price, environment and safety. As the adhesive, solvent type, emulsion type, hot melt type and the like are used, but among them, acrylic emulsion type is usually widely used from the viewpoint of safety and quality.

In recent years, such adhesive sheets have been made thin in order to minimize unnecessary parts (hereinafter referred to as "residues") around the punched labels from the viewpoint of resource saving, especially for commercial and industrial labels. Is desired. Furthermore, it is also desired to punch through complicated shapes at high speed in order to increase decorativeness and productivity. For this reason, if the release force of the release paper is not sufficiently small, the debris is likely to break when the debris is peeled off from the release paper during label processing (hereinafter referred to as "debris removal"), and there is a problem of deterioration in workability. ..

Further, in the process of applying the adhesive to the release paper, if the release paper has pinholes or recesses, the release paper becomes an adhesive sheet in a state where the adhesive is contained in the release paper. In such an adhesive sheet, when the surface base material to which the adhesive is attached is peeled from the release paper in the printing / labeling step, a phenomenon that the adhesive remains on the release paper (hereinafter referred to as "adhesive residue") can be seen.

If there is adhesive residue, the adhesive remaining on the release paper on the guide roll, etc., which hits the surface of the release paper when printing, die-cutting (punching), removing debris, etc. in the process of applying the adhesive sheet to form printing or sticker printing processing. Adheres. This causes troubles such as poor paper feed and printing misalignment, and is a serious obstacle to workability and quality. Further, in the process of printing or labeling with an auto labeler, a handler labeler, or the like, paper feed defects, print misalignment, and the like are similarly caused by adhesive residue, which causes a problem.

In order to solve this problem, in the base paper for release paper, it is an effective means to form an undercoat layer having a barrier property so that the release agent does not penetrate. Several techniques have been developed for the undercoat layer formed on the release paper base paper. Patent Document 1 discloses a base paper for release paper provided with an undercoat layer (sealing layer) containing polyvinyl alcohol (PVA) as a main component and a release layer. Patent Document 2 discloses a base paper for release paper provided with an undercoat layer and a release layer containing α-olefin-modified polyvinyl alcohol and a plate-like pigment.

Japanese Unexamined Patent Publication No. 2016-186139 JP 2015-166499

However, according to the examples described in Patent Document 1, the Oken-type air permeability of the release paper provided with the undercoat layer containing polyvinyl alcohol as a main component remains at about 5400 seconds at the maximum, and further the barrier property is improved. Is desired. Further, in the base paper for release paper described in Patent Document 2, the Oken-type air permeability is improved by the thickness of the undercoat layer, and in the example of the Oken-type high air permeability, the dry mass is 4.5 g / m. ^It has a thick undercoat layer of 2. In the coating process for release paper base paper, a method of applying a coating liquid on a paper machine (on-machine coating) is often used, but forming such a thick coating layer by on-machine coating. It is difficult.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a base paper for a release paper and a release paper capable of forming an adhesive sheet having a small peeling force due to the excellent barrier property of the undercoat layer. And.

The present inventors have made various studies on the characteristics of the base paper for release paper in order to improve the label processing suitability such as the adhesive residue of the adhesive sheet and the suitability for removing debris. As a result, it was found that if unmodified polyvinyl alcohol having a high degree of saponification and high purity is used as the resin in the undercoat layer composed of the resin and the plate-like pigment, the undercoat layer exhibits sufficient barrier properties, and the present invention has been reached. bottom.

(1) A base paper for a release paper in which an undercoat layer is provided on at least one surface of a base paper, and the undercoat layer is a plate-like non-modified polyvinyl alcohol having a saponification degree of 99.0% or more and a purity of 95% or more. A base paper for release paper containing a pigment, wherein the plate-shaped pigment has a particle size of 3.0 μm or more.

(2) The base paper for release paper according to (1), wherein the base paper is composed of pulp fibers having a disintegration freeness of 100 to 300 ml.

(3) The base paper for release paper according to (1) or (2) above, which has an air permeability of 1.1 million seconds or more.

(4) The base paper for release paper according to any one of (1) to (3) above, wherein the amount of the undercoat layer adhered is 0.5 to 4.0 g / m ^2.

(5) A release paper in which a release agent layer is provided on the undercoat layer of the base paper for release paper according to any one of (1) to (4).

According to the present invention, it is possible to provide a base paper for a release paper and a release paper capable of forming an adhesive sheet having a small peeling force due to the excellent barrier property of the undercoat layer.

Hereinafter, embodiments of the present invention will be specifically described. The description of the constituent elements described below may be based on typical embodiments or specific examples, but the present invention is not limited to such embodiments. In this specification, the numerical range represented by using "~" means a range including the numerical values before and after "~" as the lower limit value and the upper limit value.

The release paper base paper of the present embodiment is composed of a base paper and an undercoat layer provided on at least one surface of the base paper.
Hereinafter, each element constituting the release paper base paper of the present embodiment will be described.

(pulp)
Examples of the pulp used for making the base paper of the base paper for release paper of the present invention include broad-leaved bleached kraft pulp (hereinafter abbreviated as LBKP), coniferous bleached kraft pulp (hereinafter abbreviated as NBKP), used paper pulp and others. Pulp raw materials can be appropriately mixed and used.
The used paper pulp used in the present embodiment also includes deinked used paper pulp (DIP) and defective products generated in the papermaking process. Further, the other pulp raw material used in the present embodiment is not limited to wood pulp, and non-wood pulp such as hemp and kenaf, and synthetic pulp may be blended.

In order to make the thickness of the release agent layer of the release paper uniform, it is desirable that the base paper of the release paper base paper has a good texture, and in order to make the texture uniform, it is preferable that the ratio of LBKP is large. ..
Compared to NBKP, LBKP has relatively fine and short fibers, and easily forms a uniform formation with few pinholes. In order to form a uniform formation with few pinholes, the blending amount of LBKP is preferably 70% by mass or more of the total raw material pulp. If it is less than 70% by mass, the uniformity of the formation becomes insufficient and pinholes are likely to be formed, and even if the release agent resin is applied, pinholes may remain, which may cause adhesive residue. Further, if the texture is not uniform, the contact of the punching blade will not be uniform when the adhesive sheet is punched, and the label will not be cut well. As a result, a trouble (hereinafter, also referred to as “raising”) occurs in which the label that should be left on the release paper is also removed.

The Canadian standard freeness (beating degree) of the above pulp according to JIS P 8121 is preferably 100 to 300 ml. By setting the Canadian standard freedom in the range of 100 to 300 ml, it is possible to form a uniform undercoat layer in combination with the effect of the sizing agent described later, and an appropriate paper interlayer strength can be obtained.
Known methods can be used for beating pulp to prepare Canadian Standard Freeness to 100-300 ml.

By preparing the Canadian standard freeness of pulp as described above, the disintegration freeness of the base paper for release paper made from pulp can be adjusted within an appropriate range. The separation freeness of the pulp obtained by dissociating the base paper for release paper by the method according to JIS P 820-1: 2012 is preferably 100 to 300 ml.

(Filling fee)
Examples of fillers that can be added to the base paper of the base paper for release paper include titanium dioxide, kaolin, talc, heavy calcium carbonate, light calcium carbonate, calcium sulfite, gypsum, calcined kaolin, white carbon, and amorphous. Examples thereof include inorganic pigments such as silica, delaminated kaolin, diatomaceous earth, magnesium carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide and zinc hydroxide, and organic pigments such as urea / formarin resin particles and fine hollow particles. be able to. The filler contained in used paper and waste paper can also be reused. For the light transmission of the base paper for release paper, it is preferable that it is at least one selected from titanium dioxide, kaolin, talc, and calcium carbonate. Of these, kaolin is particularly preferable in order to achieve high light transmission in papermaking in the acidic pH range. Calcium carbonate dissolves under acidic conditions and is not preferable for acidic papermaking.
The light transmittance of the release paper base paper greatly affects the photocell suitability of the adhesive sheet, and the light transmission differs depending on the hue and basis weight of the release paper base paper. Further, since the strength of the base paper decreases as the blending amount of the filler increases, the blended amount of the filler is preferably 0 to 25% by mass, more preferably 0 to 20% by mass.

(Size agent)
It is preferable that the base paper of the base paper for release paper contains a sizing agent. By containing a sizing agent in the base paper, when the undercoat layer described later is applied to the base paper, the undercoat agent does not permeate too much into the inside, and a uniform undercoat layer can be provided near the surface. The sizing agent is originally added for the purpose of preventing the ink from bleeding, but it has been found that the sizing agent has the above-mentioned new effect in the present embodiment.

Specific examples of the sizing agent include rosin type, alkyl ketene dimer type, alkenyl succinic anhydride type, styrene-acrylic type, higher fatty acid type, petroleum resin type and the like. Papermaking in the acidic pH range is preferable in order to ensure printability and maintain surface properties. Rosin-based sizing agents are preferred in order to impart sufficient sizing in the acidic pH range.
The content of the sizing agent is preferably 0.3% by mass or more with respect to the base paper. If the content of the sizing agent is less than 0.3% by mass, the degree of nice human size of the base paper for release paper becomes low, and there is a possibility that an appropriate Oken-type air permeability cannot be obtained. The content of the preferred sizing agent is in the range of 0.4 to 1.5% by mass, and the content of the more preferable sizing agent is in the range of 0.5 to 1.0% by mass.

In addition to pulp, fillers, and sizing agents, the base paper for release paper base paper is used for papermaking such as paper strength enhancers, yield improvers, pH adjusters, drainage improvers, wet paper strength agents, dyes and pigments. Internal aids can be added as needed.

(Paper power enhancer)
Specific examples of the paper strength enhancer include anionic polyacrylamide, cationic polyacrylamide, amphoteric polyacrylamide, cationic starch, graft copolymers of polyacrylamide and starch, various modified starches, urea resin, and polyamide / polyamine resin. , Polyvinyl alcohol, polyethylene oxide and the like. In order to achieve high paper interlayer strength, at least one selected from anionic polyacrylamide, cationic polyacrylamide, amphoteric polyacrylamide, cationic starch, and graft copolymers of polyacrylamide and starch is preferable.

(Yield improver)
Specific examples of the yield improver include polyacrylamide-based compounds, polyethylene glycol-based compounds, and polyvinylamine-based compounds. When titanium dioxide is used as the filler, the overall yield is lowered and the productivity is likely to be lowered. Therefore, an appropriate yield improver is appropriately selected in order to maintain the productivity.

(PH regulator)
Specific examples of pH adjusters include sulfuric acid bands, aluminum chloride, sulfuric acid, hydrochloric acid, sodium aluminate, basic aluminum compounds, sodium hydroxide, potassium hydroxide, ammonia, and various primary, secondary, and tertiary pH adjusters. Examples thereof include alkaline compounds such as secondary amines. Sulfuric acid band, sulfuric acid, and sodium hydroxide are preferable from the viewpoint of versatility and economy.

(Basis weight of base paper)
The basis weight of the base paper for release paper is preferably from 30 to 150 g / ^{m 2,} more preferably from 30 to 120 g / ^{m 2,} further preferably 30 to 100 g / ^{m 2.} When the basis weight is 150 g / m ² or less, there is no possibility that the paper becomes too heavy and the workability at the time of producing the release paper is deteriorated. On the other hand, when the basis weight is 30 g / m ² or more, the strength of the release paper can be improved.

(Paper thickness of base paper)
The base paper of the base paper for release paper preferably has a paper thickness of 25 to 250 μm, more preferably 30 to 200 μm. When the paper thickness is 250 μm or less, there is no possibility that the workability at the time of producing the release paper is deteriorated due to the bulkiness being too high. On the other hand, when the paper thickness is 25 μm or more, the strength of the release paper can be improved.

(Density of base paper)
Density of release paper base paper is preferably from 0.6 to 1.2 g / cm ^3, more preferably 0.8~1.0g / cm ^3. When the density is 1.2 g / cm ³ or less, it is not necessary to make the paper thickness extremely thin, and the productivity is improved. On the other hand, when the density is 0.6 g / cm ³ or more, the strength of the release paper can be improved.

(Light transmission of base paper)
Here, for example, when printing a barcode or the like on an adhesive sheet, the position of the surface base material is detected from the difference in light transmission between the adhesive label and the release paper by a phototube. Therefore, it is preferable that the base paper for release paper has excellent light transmission.
In order to improve the light transmittance, there are methods such as high beating the pulp or papermaking of pulp mainly composed of LBKP and increasing the density of the base paper by calendar processing or the like. Among LBKPs, those containing a large amount of hemicellulose tend to exhibit light transmission.
By adjusting the content of LBKP in the pulp that composes the base paper, the Canadian standard freedom of the base paper, and the density of the base paper as described above, a base paper for release paper with sufficient light transmission is manufactured. can.

(Smoothness of base paper)
In addition, as a method for controlling the surface of the base paper of the release paper base paper to be uniformly covered with the undercoat layer, JAPAN TAPPI pulp and paper test method No. The Oken-type smoothness of the base paper measured according to 5-2: 2000 can be used. That is, if the Oken-type smoothness is less than 20 seconds, it is difficult to uniformly cover the surface of the base paper with the undercoat layer. The Oken-type smoothness of the base paper is preferably 30 seconds or longer, more preferably 80 seconds or longer.

(Oken type air permeability of base paper)
In addition, as a method for controlling the surface of the base paper of the release paper base paper to be uniformly covered with the undercoat layer, JAPAN TAPPI pulp and paper test method No. The Oken-type air permeability of the base paper measured according to 5-2: 2000 can be used. That is, if the air permeability of the Oken type is less than 20 seconds, it is difficult to uniformly cover the surface of the base paper with the undercoat layer. The Oken-type air permeability of the base paper is preferably 50 seconds or longer, more preferably 80 seconds or longer.

(Base paper size)
As a method for controlling the surface of the base paper of the release paper base paper to be uniformly covered with the undercoat layer, the degree of fine human size of the base paper measured by the white human method specified in JIS P 8122: 2004 can be used. .. That is, the degree of stekihito size of the base paper is preferably 3 to 50 seconds, more preferably 5 to 40 seconds.

(Undercoat layer)
An undercoat layer is provided on at least one surface of the base paper of the base paper for release paper in order to control the release agent resin to stay uniformly on the surface of the base paper.
In this embodiment, the undercoat layer contains unmodified polyvinyl alcohol and a plate pigment.

(Non-denatured polyvinyl alcohol)
As will be described later, the polyvinyl alcohol used in the base paper for release paper of the present embodiment is required to have high purity and saponification degree and contain a large amount of OH groups from the viewpoint of improving the effect of suppressing adhesive residue. Therefore, in this embodiment, an unmodified polyvinyl alcohol in which the OH group is not substituted is used. Details of the purity and saponification degree of polyvinyl alcohol will be described later.
As a component of the main chain of the unmodified polyvinyl alcohol, a polymer obtained by saponifying a polymer containing a vinyl ester typified by a vinyl acetate monomer is preferably used.

In producing unmodified polyvinyl alcohol, vinyl esters other than vinyl acetate, such as vinyl formate, vinyl acrylate, vinyl butyrate, vinyl crotonate, vinyl chloroacetate, vinyl oleate, vinyl propionate, vinyl caproate, capryl Saturated fatty acid vinyl esters such as vinyl acetate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl pivalate, vinyl versaticate can be used in place of vinyl acetate.

The purity of the non-modified polyvinyl alcohol in the present embodiment is 95% or more, and 96% or more, from the viewpoint of suppressing the permeation of the release agent resin and exerting the effect of suppressing the adhesive residue to a higher degree. Is more preferable. Here, the purity refers to the mass ratio of the vinyl alcohol unit among the monomer units constituting polyvinyl alcohol.
As the purity of the unmodified polyvinyl alcohol increases, the number of comonomer having no OH group decreases, so that the number of OH groups in the unmodified polyvinyl alcohol increases. Then, the interaction between the OH group in the unmodified polyvinyl alcohol and the plate-like pigment is promoted, the bond between the two is strengthened, and it is presumed that this contributes to the improvement of the barrier property of the undercoat layer.

The degree of saponification of the non-modified polyvinyl alcohol in the present embodiment needs to be sufficiently saponified from the viewpoint of suppressing the permeation of the release agent resin and exerting the effect of suppressing the adhesive residue to a higher degree. That is, it should be 99.0% or more, more preferably 99.4% or more, in terms of the molar ratio of the saponified ester group to the ester group that was present before the saponification.
As the saponification of the unmodified polyvinyl alcohol progresses, the ester groups in the unmodified polyvinyl alcohol are hydrolyzed and the number of OH groups increases. Then, it is presumed that the interaction between the OH group in the unmodified polyvinyl alcohol and the plate-like pigment is promoted, the bond between the two is strengthened, and the barrier property of the undercoat layer is improved.

Such a highly pure and highly saponified non-denatured polyvinyl alcohol can not only enhance the barrier property of the undercoat layer, but also suppress the generation of the sour odor peculiar to polyvinyl alcohol. Therefore, the release paper base paper of the present embodiment and the release paper using the same are excellent not only in excellent workability but also excellent in suitability for labels used for products that are desirable to be odorless, for example, food containers and the like. ..

The degree of polymerization of the unmodified polyvinyl alcohol in the present embodiment is preferably in the range of 200 to 8000 from the viewpoint of solvent resistance and punching suitability. It is more preferably in the range of 300 to 2500, even more preferably in the range of 400 to 2000, and most preferably in the range of 500 to 1800.

(Plate pigment)
In the undercoat layer used in the present embodiment, it is necessary to mix a plate-like pigment with unmodified polyvinyl alcohol. In the case of close-packing the pigment, the porosity is generally reduced and a dense coating layer can be formed by using the plate-shaped pigment as compared with the spherical pigment, which is preferable in terms of quality.

There are no particular restrictions on the type of plate pigment, and inorganic pigments such as kaolin, talc, illite, mica, artificial mica, calcium carbonate, titanium dioxide, aluminum hydroxide, and silica can be appropriately selected and used. Of these, those having an aspect ratio of 7 or more are preferable. Since the plate-like pigment having an aspect ratio of 7 or more is oriented in the plane direction during coating, a coating layer having excellent barrier properties and smoothness can be easily obtained.
Here, the aspect ratio can be obtained by measuring the thickness of the flat pigment by electron microscope observation and dividing the volume average particle diameter of the flat pigment by the thickness.
Examples of the plate-like pigment having an aspect ratio of 7 or more preferably used in the present embodiment include kaolin, talc, illite, mica, artificial mica, aluminum hydroxide and the like.

It is desirable that the plate-shaped pigment has a large particle size (median size) because it has excellent barrier properties and smoothness. Since the plate-shaped pigment having a large particle size can reduce the gap between the plate-shaped pigments, it can contribute to the improvement of the barrier property. Therefore, the plate-shaped pigment needs to have a particle size of 3.0 μm or more, and preferably 3.1 μm or more. Further, the plate-like pigment preferably has excellent light transmission. At this time, the particle size can be determined using, for example, a laser diffraction / scattering type particle size distribution meter (manufactured by HORIBA, “LA-300”).

The blending amount of the plate pigment and the unmodified polyvinyl alcohol is preferably in the range of 50 to 300 parts by mass with respect to 100 parts by mass of the plate pigment. If the blending amount of the unmodified polyvinyl alcohol exceeds 300 parts by mass, the cylinder dryer is significantly contaminated immediately after coating, and the pinholes are not sufficiently covered with the plate-like pigment, so that the effect of improving the adhesive residue may not be exhibited. be. On the other hand, if the blending amount of the unmodified polyvinyl alcohol is less than 50 parts by mass, the pigment and the voids of the pigment cannot be sufficiently filled with the unmodified polyvinyl alcohol, and a large number of fine voids are generated. Permeation into the substrate may not be suppressed.

The amount of the undercoat layer applied is preferably ^{0.5 to 4.0 g / m 2} with respect to the base paper for release paper after drying. If it is less than 0.5 g / m ² , the effect of preventing the release agent resin from penetrating becomes insufficient, and the release force tends to increase. If the amount of the undercoat layer applied is ^{more than 4.0 g / m 2} , the peeling force becomes too small and the body tends to rise.
The amount of coating in such a range is an amount that can be easily realized even with on-machine coating, which is often used in the actual manufacturing process of release paper. The release paper base paper of the present embodiment can obtain a release force with an undercoat layer having a coating amount that is easy to realize even with on-machine coating.

In this way, the plate-shaped pigment having a high aspect ratio and a large particle size efficiently covers the surface of the base paper of the release paper base paper, and polyvinyl alcohol fills the fine gaps between the plate-shaped pigments. An undercoat layer having a high barrier property can be realized. The base paper for release paper having an undercoat layer having a high barrier property suppresses the release agent from penetrating into the inside when the release agent is applied, and can form a uniform release agent layer on the surface. As a result, it is possible to obtain a release paper having a small peeling force and excellent label processing suitability.

(Manufacturing method of base paper)
A method for producing a base paper for a release paper base paper of the present embodiment will be described.
In the present embodiment, an undercoat layer containing unmodified polyvinyl alcohol and a plate-like pigment is applied to at least one surface of the above-mentioned base paper.

As a method of applying the undercoating agent, a generally known coating device can be used. Examples of coating equipment include blade coaters, air knife coaters, roll coaters, reverse roll coaters, bar coaters, curtain coaters, slot die coaters, gravure coaters, champlex coaters, brush coaters, slide bead coaters, two rolls or rod metas. Examples include a ring type size press coater, a pound size press coater, a bill rod metering size press coater, a short dwell coater, a gate roll coater, and a calender nip coater. Among these, film transfer coaters such as rod metering type size press coaters and gate roll coaters, bar coaters, and blade coaters that can apply different types of primer to both sides of the base paper at the same time online. Is preferably used.

Further, in the present embodiment, it is possible to increase the density of the release paper base paper by applying the undercoat layer to the base paper, drying it, and smoothing it with a calendar roll. The light transmission of the base paper can be improved. In addition, the undercoat layer can be made to have excellent barrier properties with few pinholes, and it is possible to prevent the release agent and the adhesive from penetrating into the base paper for the release paper. Here, as the calendar processing, it is preferable to use a plurality of calendar rolls including a metal roll and a resin roll.

Further, as the calendar processing, considering the development of light transmission, ^{it is preferable that the density is in the range of 1.0 to 1.2 g / cm 3} , so high temperature multi-stage pressurization by a super calendar that makes it easier to increase the density. Treatment is preferred. The super calendar refers to a method in which calendar rolls composed of metal rolls and resin rolls are alternately arranged in about 10 to 20 stages to continuously perform calendar processing.

When the smoothing treatment is performed using a calendar roll, it is preferable to perform the smoothing treatment in a state where the base paper for release paper retains 10 to 20% by mass of water because it is easy to increase the density.

(Oken type air permeability of base paper for release paper)
As a method for controlling the barrier property, the JAPAN TAPPI pulp and paper test method No. The Oken-type air permeability of the base paper for release paper measured according to 5-2: 2000 can be used. If the Oken-type air permeability of the base paper for release paper is less than 10,000 seconds, the release agent resin permeates too much and it becomes difficult to develop the release performance. The Oken-type air permeability of the base paper for release paper is preferably 50,000 seconds or more, more preferably 80,000 seconds or more, and particularly preferably 1,100,000 seconds or more.

As described above, the base paper for release paper of the present embodiment has the separation freeness of the pulp constituting the base paper within a predetermined range, and as the undercoat layer, high-purity and high saponification-free polyvinyl alcohol and particle size. And a plate-like pigment having a large aspect ratio is used. By doing so, it is possible to form an undercoat layer near the surface of the base paper that suppresses the penetration of the release agent into the inside, and to uniformly form the release agent layer near the surface of the base paper for release paper. .. Further, it is possible to reduce the amount of the release agent such as silicone resin used for forming the release agent layer without lowering the release effect.

(Manufacturing method of release paper)
In the present embodiment, a release agent resin is applied to a release paper base paper in the above paper quality range and dried to form a release agent layer to form a release paper. As the release agent resin in the present embodiment, silicone resin, fluororesin, aminoalkyd resin, polyester resin and the like can be generally exemplified, but usually, in terms of release quality and price, an aqueous emulsion type, a solvent type or a solvent-free type can be exemplified. Silicone resin is used. In particular, in terms of environmental friendliness and worker safety, switching to the aqueous emulsion type and the solvent-free type is progressing, and in this embodiment, it is more preferable to use the solvent-free silicone resin. Of these, a solvent-free silicone resin having a viscosity at 25 ° C. of 50 to 1,000 mPa · s is more preferable. Examples of the method for applying the release agent resin include a bar coater, an air knife coater, a direct gravure coater, an offset gravure coater, and a multi-stage roll coater.

The amount of the release agent resin applied is preferably ^{0.5 to 1.5 g / m 2.} If the coating amount is ^{less than 0.5 g / m 2} , the amount of the release agent is small and the release performance is insufficient, and there is a possibility that the debris breaks frequently during label processing. On the other hand, ^{if the amount exceeds 1.5 g / m 2} , the peeling force becomes too small, and there is a risk that the person will rise frequently. Further, as described above, when the uniformity of the formation after the release paper is quantified as the formation unevenness by the transmitted light, the standard deviation thereof is preferably 0.4 or less. When it becomes larger than 0.4, the texture unevenness gradually becomes large, which causes non-uniformity of the blade contact during punching, and the label processing suitability deteriorates. Further, it is preferable to increase the compressive elastic modulus in the thickness direction of the release paper to improve the punching suitability, and from that point of view, it is preferable to increase the density of the release paper.

(Manufacturing method of adhesive sheet)
When the pressure-sensitive adhesive sheet is manufactured, the pressure-sensitive adhesive is applied to the surface of the release agent layer of the release paper, dried, and then bonded to the surface base material to form the pressure-sensitive adhesive sheet. As the pressure-sensitive adhesive, for example, rubber-based adhesives such as natural rubber, styrene-butadiene copolymer, styrene-isopropylene block copolymer, recycled rubber and synthetic rubber, acrylic-based and silicone-based pressure-sensitive adhesives are appropriately used. .. These pressure-sensitive adhesives are in the form of solvent type, aqueous emulsion type, hot melt type, liquid curing type and the like. The amount of the pressure-sensitive adhesive applied is appropriately adjusted in the range of ^{10 to 40 g / m 2 in terms of dry mass.} If the amount of the adhesive applied is ^{less than 10 g / m 2} , the adhesive strength becomes too low, and the label may float when the label is attached to various adherends. If the amount of the adhesive applied exceeds 40 g / m ² , the adhesive may protrude from the cross section of the adhesive sheet during the punching process of the label, and the adhesive may accumulate to stain or damage the printed surface of the label. Examples of the method of applying the adhesive include a reverse roll coater, a reverse gravure coater, a vario gravure coater, a knife coater, a bar coater, a die coater, and a curtain coater.

Examples of the surface base material include cast-coated paper, art paper, coated paper, wood-free paper, thermal paper, inkjet paper, synthetic paper, vapor-deposited paper, various polymer films, etc., and are appropriately selected according to the application and purpose. Can be used.

A release paper with a release agent layer on a release paper base paper that has an undercoat layer prepared and coated with a specific pigment and polyvinyl alcohol. Obtainable.
Further, the release paper base paper of the present embodiment and the release paper using the same have not only excellent workability but also an effect of suppressing an sour odor. Therefore, this embodiment is excellent in suitability for products that are desirable to be odorless, such as labels used for food containers and the like.

This embodiment will be described in more detail with reference to the following examples. Unless otherwise specified, parts and% in Examples and Comparative Examples indicate parts by mass and% by mass, respectively, and the coating amount, number of parts, mixing ratio, etc. are all indicated by solid content.

<Non-denatured polyvinyl alcohol 1>
An unmodified polyvinyl alcohol manufactured by Japan Vam & Poval Co., Ltd., having a saponification degree of 99.4% or more, a purity of 96.0% or more, a degree of polymerization of 1700, and a trade name of "VI" was used. This is almost completely saponified polyvinyl alcohol.

<Non-denatured polyvinyl alcohol 2>
An unmodified polyvinyl alcohol manufactured by Kuraray, having a saponification degree of 98.0 to 99.0%, a purity of 94.0% or more, a degree of polymerization of 1700, and a trade name of "117BU" was used. This is almost completely saponified polyvinyl alcohol.

<Non-denatured polyvinyl alcohol 3>
An unmodified polyvinyl alcohol manufactured by Kuraray, having a saponification degree of 87.0 to 89.0%, a purity of 94.0% or more, a degree of polymerization of 1700, and a trade name of "217" was used. This is a partially saponified polyvinyl alcohol.

<Ethylene-modified polyvinyl alcohol 1>
Ethylene-modified polyvinyl alcohol manufactured by Kuraray, having a saponification degree of 95.5 to 97.5%, a purity of 94.0% or more, a degree of polymerization of 1700, and a trade name of "RS2817" was used.

<Ethylene-modified polyvinyl alcohol 2>
Ethylene-modified polyvinyl alcohol manufactured by Kuraray, having a saponification degree of 99.0 to 99.6%, a purity of 94.0% or less, a degree of polymerization of 1000, and a trade name of "HR3010" was used. It is a nearly completely saponified polyvinyl alcohol, but with the lowest purity and degree of polymerization of the Examples and Comparative Examples.

(Example 1)

<Base paper for release paper>
Cationic starch (trade name: "Piller Starch P-3T", manufactured by Pillar Starch Co., Ltd.) as a paper strength agent for absolute dry pulp in a pulp slurry of Canadian Standard Freeness 250 ml consisting of 100 parts of LBKP. After adding 5%, rosin sizing agent (trade name: "Size Pine N-776", manufactured by Arakawa Chemical Industry Co., Ltd.) 0.5% and sulfuric acid band 1.0% as sizing agent and fixing, Nagami paper machine Paper was made at a paper making concentration of 0.3%, and a base paper for a base paper for release paper was obtained.
The humidity control basis weight of the base paper of the obtained release paper base paper is 43.8 g / m ² , the paper thickness according to JIS P 8118 is 52.7 μm, the density according to JIS P 8118 is 0.83 g / cm ³ , and JIS P 8155. The smoothness of the Oken type was 70/49 seconds, and the Japanese Industrial Standards Pulp Test Method No. According to 5-2: 2000, the air permeability of the Oken type was 22 seconds, and that of JIS P 8122 was 7 seconds.

<Undercoat layer>
The unmodified polyvinyl alcohol 1 was used as the polyvinyl alcohol on the base paper, and 100 parts by mass of polyvinyl alcohol and kaolin (trade name: "HT clay", aspect ratio 7, particle size 3. 1 μm, manufactured by Engelhard Co., Ltd.) 100 parts by mass of an 11% mixed solution was applied, ^{and an undercoat layer having a dry mass of 1.5 g / m 2} was provided to obtain a base paper for release paper.

(Comparative Example 1)
The non-modified polyvinyl alcohol 2 was used as the polyvinyl alcohol on the base paper of Example 1, the coating amount was 1.4 g / m ² in terms of dry mass, and an undercoat layer was provided in the same manner as in Example 1 except for these. Obtained a base paper for release paper.

(Comparative Example 2)
The non-modified polyvinyl alcohol 3 was used as the polyvinyl alcohol on the base paper of Example 1, the coating amount was 1.4 g / m ² in terms of dry mass, and an undercoat layer was provided in the same manner as in Example 1 except for these. Obtained a base paper for release paper.

(Comparative Example 3)
A base paper for release paper was obtained by providing an undercoat layer in the same manner as in Example 1 except that the ethylene-modified polyvinyl alcohol 1 was used as the polyvinyl alcohol on the base paper of Example 1.

(Comparative Example 4)
The ethylene-modified polyvinyl alcohol 2 was used as the polyvinyl alcohol on the base paper of Example 1, the coating amount was 1.4 g / m ² in terms of dry mass, and an undercoat layer was provided in the same manner as in Example 1 except for these. Obtained a base paper for release paper.

(Comparative Example 5)
A 12% mixture of 100 parts by mass of polyvinyl alcohol and 100 parts by mass of kaolin was used as the base paper of Example 1 with an aspect ratio of 7 as kaolin, a particle size of 0.3 μm, and the trade name “Kaofine” manufactured by Seal. After coating, an undercoat layer was provided in the same manner as in Example 1 except for these to obtain a base paper for release paper.

(Comparative Example 6)
The ethylene-modified polyvinyl alcohol 1 is used as the polyvinyl alcohol and the "kaolin" is used as the kaolin on the base paper of Example 1, and a 12% mixed solution of 100 parts by mass of polyvinyl alcohol and 100 parts by mass of kaolin is applied. However, a base paper for release paper was obtained by providing an undercoat layer in the same manner as in Example 1 except for these.

(Comparative Example 7)
The non-modified polyvinyl alcohol 1 was used as the polyvinyl alcohol on the base paper of Example 1 and a 5% mixed solution of polyvinyl alcohol was applied to adjust the coating amount to 0.5 g / m ^{2 in terms of dry mass.} An undercoat layer was provided in the same manner as in Example 1 except for the above, and a base paper for release paper was obtained.

(Comparative Example 8)
The non-modified polyvinyl alcohol 2 was used as the polyvinyl alcohol on the base paper of Example 1 and a 5% mixed solution of polyvinyl alcohol was applied to adjust the coating amount to 0.5 g / m ^{2 in terms of dry mass.} An undercoat layer was provided in the same manner as in Example 1 except for the above, and a base paper for release paper was obtained.

(Comparative Example 9)
The non-modified polyvinyl alcohol 3 was used as the polyvinyl alcohol on the base paper of Example 1 and a 5% mixed solution of polyvinyl alcohol was applied to adjust the coating amount to 0.5 g / m ^{2 in terms of dry mass.} An undercoat layer was provided in the same manner as in Example 1 except for the above, and a base paper for release paper was obtained.

(Comparative Example 10)
The ethylene-modified polyvinyl alcohol 1 was used as the polyvinyl alcohol on the base paper of Example 1 and a 5% mixed solution of polyvinyl alcohol was applied to adjust the coating amount to 0.5 g / m ^{2 in terms of dry mass.} An undercoat layer was provided in the same manner as in Example 1 except for the above, and a base paper for release paper was obtained.

(Comparative Example 11)
The ethylene-modified polyvinyl alcohol 2 was used as the polyvinyl alcohol on the base paper of Example 1 and a 5% mixed solution of polyvinyl alcohol was applied to adjust the coating amount to 0.4 g / m ^{2 in terms of dry mass.} An undercoat layer was provided in the same manner as in Example 1 except for the above, and a base paper for release paper was obtained.

The measurement / evaluation results for Example 1 and Comparative Examples 1 to 11 are shown in Table 1.
The Oken-type air permeability of the base paper for release paper, that is, the barrier property of the undercoat layer was evaluated.

As is clear from Table 1, Example 1 in which the undercoat layer was formed by using unmodified polyvinyl alcohol having high purity and high saponification degree and a flat pigment having a large particle size was compared with Comparative Examples 1 to 11. It showed outstanding high air permeability and was excellent in barrier properties.

The effects of polyvinyl alcohol saponification and purity on the barrier properties of the undercoat layer will be considered.
Comparison of Example 1 and Comparative Examples 1 and 2 using unmodified polyvinyl alcohol is performed. The only difference between Comparative Examples 1 and 2 is the degree of saponification of the unmodified polyvinyl alcohol, and Comparative Example 1 having a high degree of saponification expresses a Wangken-type air permeability that is 15 times or more that of Comparative Example 2 having a low degree of saponification. ..
From this, it can be seen that the unmodified polyvinyl alcohol having a high degree of saponification is effective in improving the barrier property of the undercoat layer.
In Example 1, both the saponification degree and the purity of the unmodified polyvinyl alcohol are higher than those in Comparative Example 1, and Example 1 exhibits a Wangken-type air permeability that is more than twice that of Comparative Example 1. The Oken-type air permeability of Example 1 of 2 million seconds is a limit value of the measuring device, and it is considered that the actual Oken-type air permeability is higher. From this, it can be seen that not only the saponification degree of polyvinyl alcohol but also the purity contributes to the improvement of the barrier property.

Consider the effect of the presence of pigments on the barrier properties of the undercoat layer.
The only difference between Comparative Examples 5 and 7 is the presence or absence of the pigment. Comparative Example 5 containing 50% by mass of the pigment exhibits 130 times or more the Oken-type air permeability as compared with Comparative Example 7 containing no pigment.
From this, it can be seen that the bond between polyvinyl alcohol and the pigment is effective in improving the barrier property of the undercoat layer.

Consider the particle size of the pigment suitable for the undercoat layer.
The only difference between Example 1 and Comparative Example 5 is the particle size of the pigment, and Example 1 using HT clay having a large particle size is more than twice as large as that of Comparative Example 5 using Kaofine having a small particle size. It expresses the laboratory-type air permeability. The Oken-type air permeability of Example 1 of 2 million seconds is a limit value of the measuring device, and it is considered that the actual Oken-type air permeability is higher. From this, it can be seen that the pigment having a large particle size has a high effect of improving the barrier property of the undercoat layer.

Claims (5)

A base paper for release paper having an undercoat layer provided on at least one surface of the base paper.
The undercoat layer contains unmodified polyvinyl alcohol having a saponification degree of 99.0% or more and a purity of 95% or more, and a plate-like pigment.
The plate-shaped pigment is a base paper for release paper characterized by having a particle size of 3.0 μm or more. The base paper for a release paper according to claim 1, wherein the base paper is made of pulp fibers having a disintegration freeness of 100 to 300 ml. The base paper for release paper according to claim 1 or 2, wherein the Oken type air permeability is 1.1 million seconds or more. The base paper for release paper according to any one of claims 1 to 3, wherein the amount of the undercoat layer adhered is 0.5 to 4.0 g / m ^2. A release paper in which a release agent layer is provided on the undercoat layer of the release paper base paper according to any one of claims 1 to 4.